Climate change is recognized as a significant problem that has received considerable attention. As a result of worldwide generation of energy from fossil fuels, large amounts of greenhouse gases are accumulating in our atmosphere. Many experts believe that if something is not done soon to slow or even reverse this accumulation, our climate and the world in which we live will suffer catastrophic consequences. Experts predict that a rise in global temperatures of just a few degrees will melt polar ice, and result in a rise of sea levels enough to put many coastal cities under water. The extinction of many species of plants and animals is also predicted by some scientists. In view of these and other significant adverse effects from burning fossil fuels to generate energy, there is a significant need for a method and apparatus that can generate energy in a cost-effective manner without the generation of significant greenhouse gases.
Solar energy systems are unlikely to have a significant impact on reducing greenhouse gases in the atmosphere until electricity can be generated using solar energy at a cost that is competitive with electricity generated by burning fossil fuels. Cost is critical to solar energy systems. In fact, cost cannot be over emphasized, because it is so important that cost alone can make the difference between success and failure. As long as solar generated electricity costs more than electricity generated by burning fossil fuels, there is little chance that solar power is going to have a significant impact on reducing greenhouse gases in our atmosphere. There has been a long felt need for an apparatus and method of manufacture for a solar conversion system that has a low total system cost and that is capable of generating electricity at a cost that is competitive with electricity generated by burning fossil fuels.
In the past, efforts at generating solar electricity directly from photovoltaic cells have not been entirely satisfactory, due to relatively high capital cost, particularly as compared with alternative methods of generation of electricity. Utility scale applications of solar energy have mostly used thermal systems where solar rays were concentrated to provide heat that was then converted into electricity through use of an engine driving an electromagnetic generator. Thermal systems have commonly used large optical reflectors to heat a working fluid with focused sunlight. Conversion efficiency was relatively low in systems with sunlight concentrated to only moderate levels in one dimension by trough reflectors.
Photovoltaic conversion with multijunction cells has been used to generate electricity from sunlight, including arrangements with sunlight concentration to improve efficiency, but the cost of complete concentrating photovoltaic systems was too high to be commercially competitive. An underlying reason for this high cost has been that, in most previous attempts using concentrating photovoltaic systems, the unit for concentration and conversion of solar power has been too small, consisting typically of one photovoltaic cell powered by one small mirror or lens to focus sunlight on the cell. Small units were preferred for converting concentrated sunlight into electricity because at small size they could be simply and passively cooled, and single cells are readily made insensitive to tracker pointing errors, but they were expensive to manufacture and deploy on the huge scale needed for utility scale power. Because the relatively high cost of such previous devices using concentrating photovoltaic systems was not competitive, such devices have had little impact and account for only a very small fraction of the total electricity generated annually.
There has been a long felt need for a system of photovoltaic generators that deliver high power concentrated sunlight at low cost per unit of power, and which can generate electricity from sunlight at a cost that is competitive with alternative conventional methods of generating electricity by burning fossil fuels.